La proliferacion de las algas marinas son un factor determinante para la salud de los arrecifes, ... more La proliferacion de las algas marinas son un factor determinante para la salud de los arrecifes, sumado a los efectos causados por la mano del hombre, haciendo que el mantenimiento y sobrevivencia de los mismos sea perjudicial en la calidad de vida de los mismos y por ende de las comunidades que dependen de este. Es fundamental entender las causas de la proliferacion de algas en los arrecifes para garantizar la proteccion de los arrecifes y el control que se debe realizar a las diferentes variables ecologicas.
Context Gamay is a coastal waterway of immense social, cultural and ecological value. Since Europ... more Context Gamay is a coastal waterway of immense social, cultural and ecological value. Since European settlement, it has become a hub for industrialisation and human modification. There is growing desire for ecosystem-level management of urban waterways, but such efforts are often challenged by a lack of integrated knowledge. Aim and methods We systematically reviewed published literature and traditional ecological knowledge (TEK), and consulted scientists to produce a review of Gamay that synthesises published knowledge of Gamay’s aquatic ecosystem to identify knowledge gaps and future research opportunities. Key results We found 577 published resources on Gamay, of which over 70% focused on ecology. Intertidal rocky shores were the most studied habitat, focusing on invertebrate communities. Few studies considered multiple habitats or taxa. Studies investigating cumulative human impacts, long-term trends and habitat connectivity are lacking, and the broader ecological role of artifi...
Drawing Sydney discusses the visual contours of a global city on the West Pacific Rim. Building o... more Drawing Sydney discusses the visual contours of a global city on the West Pacific Rim. Building on new research on city branding, the paper discusses how the image-ability or idea of the city may be gauged through visually oriented research methodologies. It is particularly ...
The eukaryotic algae display a spectacular diversity of light harvesting pigments and photosynthe... more The eukaryotic algae display a spectacular diversity of light harvesting pigments and photosynthetic mechanisms. By contrast the Cyanobacteria on one side and the land plants on the other are uniformly dull. The Cyanobacteria make up for this relative uniformity in just one way: they have a much greater range of chlorophyll pigments, and in the case of chlorophyll d, this pigment does nearly all the heavy lifting in photosynthesis. The plastids of eukaryotic algae arose by endosymbiosis from Cyanobacteria, but during this phase of evolution, which lasted perhaps 1.5 billion years, many new structures and pigments evolved, giving the basis for the overall diversity. Three types of primary plastids occur today, the chloroplasts (Chlorophyta), the rhodoplasts (Rhodophyta) and the glaucoplasts (Glaucophyta), each with characteristic pigments and photosynthetic mechanisms. These primary lines became secondarily endosymbiotic, giving rise to secondary plastids and several evolutionary lines of eukaryotic algae. Here mention should be made of lines with chlorophyll c such as diatoms, with fucoxanthin as a main pigment, dinoflagellates with peridinin and other major members of the oceanic phytoplankton with a range of carotenoid pigments. And moving further down the evolutionary road one comes to the apicomplexans, which have lost their photosynthetic capacity but which retain an apicoplast and are important pathogens, such as the malaria organism. In all these photosynthetic, eukaryotic algae there has also been a development of mechanisms to cope with variable light, generally known as non-photochemical quenching, which is developed to a much greater extent compared to Cyanobacteria.
This review discusses the evidence for the involvement of superoxide radical, hydrogen peroxide a... more This review discusses the evidence for the involvement of superoxide radical, hydrogen peroxide and singlet oxygen (reactive oxygen species, ROS) as triggers for coral bleaching. While these potential triggers have been suggested frequently over the last 25 years, there has been much progress in recent times which sustains these arguments. This review points out the recent evidence on the generation of superoxide, hydrogen peroxide and singlet oxygen in isolated Symbiodiniaceae cells and in corals. The primary site for the production of superoxide and hydrogen peroxide is likely to be close to Photosystem I (PSI) and involve the Mehler-Ascorbate-Peroxidase (MAP) pathway, but direct involvement of ferredoxin is also possible. Furthermore, the role of flavodiiron complexes has not been explored, and these are likely to act in buffering over-reduction of PSI, but are likely overcome under bleaching conditions. The whole system around PSI needs much closer scrutiny. Hydrogen peroxide and even singlet oxygen have been shown to be able to permeate the plastid membrane and even the Symbiodinium (Symbiodiniaceae) symbiosome membrane. So they are potential triggers for second messenger (cascade) processes. Unfortunately, there is little evidence at present as to whether coral bleaching can be triggered by second messenger systems generated in the zooxanthellae or in the host, or in both, and much more work needs to be done in future in validating any of these triggering hypotheses.
Abstract An in situ reef fertilization experiment is being undertaken on the Australian Great Bar... more Abstract An in situ reef fertilization experiment is being undertaken on the Australian Great Barrier Reef, to investigate the response of coral reefs to nutrient enrichment. This experiment, known as ENCORE, is designed to quantify the fate of nitrogen and phosphorus within a coral reef, and compare their impact on a variety of coral reef organisms. Co-ordinated by the Great Barrier Reef Marine Park Authority (GBRMPA), 30 scientists from eight Australian and three overseas organizations are undertaking research encompassing cellular through to community level responses. This research will provide a scientific basis for developing appropriate water quality management strategies in coral reef environments, and may identify a number of sub-lethal indicators of nutrient stress.
La proliferacion de las algas marinas son un factor determinante para la salud de los arrecifes, ... more La proliferacion de las algas marinas son un factor determinante para la salud de los arrecifes, sumado a los efectos causados por la mano del hombre, haciendo que el mantenimiento y sobrevivencia de los mismos sea perjudicial en la calidad de vida de los mismos y por ende de las comunidades que dependen de este. Es fundamental entender las causas de la proliferacion de algas en los arrecifes para garantizar la proteccion de los arrecifes y el control que se debe realizar a las diferentes variables ecologicas.
Context Gamay is a coastal waterway of immense social, cultural and ecological value. Since Europ... more Context Gamay is a coastal waterway of immense social, cultural and ecological value. Since European settlement, it has become a hub for industrialisation and human modification. There is growing desire for ecosystem-level management of urban waterways, but such efforts are often challenged by a lack of integrated knowledge. Aim and methods We systematically reviewed published literature and traditional ecological knowledge (TEK), and consulted scientists to produce a review of Gamay that synthesises published knowledge of Gamay’s aquatic ecosystem to identify knowledge gaps and future research opportunities. Key results We found 577 published resources on Gamay, of which over 70% focused on ecology. Intertidal rocky shores were the most studied habitat, focusing on invertebrate communities. Few studies considered multiple habitats or taxa. Studies investigating cumulative human impacts, long-term trends and habitat connectivity are lacking, and the broader ecological role of artifi...
Drawing Sydney discusses the visual contours of a global city on the West Pacific Rim. Building o... more Drawing Sydney discusses the visual contours of a global city on the West Pacific Rim. Building on new research on city branding, the paper discusses how the image-ability or idea of the city may be gauged through visually oriented research methodologies. It is particularly ...
The eukaryotic algae display a spectacular diversity of light harvesting pigments and photosynthe... more The eukaryotic algae display a spectacular diversity of light harvesting pigments and photosynthetic mechanisms. By contrast the Cyanobacteria on one side and the land plants on the other are uniformly dull. The Cyanobacteria make up for this relative uniformity in just one way: they have a much greater range of chlorophyll pigments, and in the case of chlorophyll d, this pigment does nearly all the heavy lifting in photosynthesis. The plastids of eukaryotic algae arose by endosymbiosis from Cyanobacteria, but during this phase of evolution, which lasted perhaps 1.5 billion years, many new structures and pigments evolved, giving the basis for the overall diversity. Three types of primary plastids occur today, the chloroplasts (Chlorophyta), the rhodoplasts (Rhodophyta) and the glaucoplasts (Glaucophyta), each with characteristic pigments and photosynthetic mechanisms. These primary lines became secondarily endosymbiotic, giving rise to secondary plastids and several evolutionary lines of eukaryotic algae. Here mention should be made of lines with chlorophyll c such as diatoms, with fucoxanthin as a main pigment, dinoflagellates with peridinin and other major members of the oceanic phytoplankton with a range of carotenoid pigments. And moving further down the evolutionary road one comes to the apicomplexans, which have lost their photosynthetic capacity but which retain an apicoplast and are important pathogens, such as the malaria organism. In all these photosynthetic, eukaryotic algae there has also been a development of mechanisms to cope with variable light, generally known as non-photochemical quenching, which is developed to a much greater extent compared to Cyanobacteria.
This review discusses the evidence for the involvement of superoxide radical, hydrogen peroxide a... more This review discusses the evidence for the involvement of superoxide radical, hydrogen peroxide and singlet oxygen (reactive oxygen species, ROS) as triggers for coral bleaching. While these potential triggers have been suggested frequently over the last 25 years, there has been much progress in recent times which sustains these arguments. This review points out the recent evidence on the generation of superoxide, hydrogen peroxide and singlet oxygen in isolated Symbiodiniaceae cells and in corals. The primary site for the production of superoxide and hydrogen peroxide is likely to be close to Photosystem I (PSI) and involve the Mehler-Ascorbate-Peroxidase (MAP) pathway, but direct involvement of ferredoxin is also possible. Furthermore, the role of flavodiiron complexes has not been explored, and these are likely to act in buffering over-reduction of PSI, but are likely overcome under bleaching conditions. The whole system around PSI needs much closer scrutiny. Hydrogen peroxide and even singlet oxygen have been shown to be able to permeate the plastid membrane and even the Symbiodinium (Symbiodiniaceae) symbiosome membrane. So they are potential triggers for second messenger (cascade) processes. Unfortunately, there is little evidence at present as to whether coral bleaching can be triggered by second messenger systems generated in the zooxanthellae or in the host, or in both, and much more work needs to be done in future in validating any of these triggering hypotheses.
Abstract An in situ reef fertilization experiment is being undertaken on the Australian Great Bar... more Abstract An in situ reef fertilization experiment is being undertaken on the Australian Great Barrier Reef, to investigate the response of coral reefs to nutrient enrichment. This experiment, known as ENCORE, is designed to quantify the fate of nitrogen and phosphorus within a coral reef, and compare their impact on a variety of coral reef organisms. Co-ordinated by the Great Barrier Reef Marine Park Authority (GBRMPA), 30 scientists from eight Australian and three overseas organizations are undertaking research encompassing cellular through to community level responses. This research will provide a scientific basis for developing appropriate water quality management strategies in coral reef environments, and may identify a number of sub-lethal indicators of nutrient stress.
The cyanobacterium Acaryochloris marina is an exceptional organism utilising chlorophyll d (Chl d... more The cyanobacterium Acaryochloris marina is an exceptional organism utilising chlorophyll d (Chl d) as its major photosynthetic pigment. Acaryochloris cells contain 90–99% Chl d with minor amounts of chlorophyll a and a chlorophyll c-like pigment. These unusual characteristics make it an excellent candidate to study various aspects of photosynthesis driven by Chl d. However, little is known about the pathway of Chl d biosynthesis. We specifically designed HPLC methods to analyse pigment compositions of Acaryochloris. This enabled us to detect intermediate products of the chlorophyll biosynthesis. We identified Mg-Protoporphyrin IX monomethyl ester (MgPMe) and Mg-2,4-divinyl pheoporphyrin (MgDVP) and the environmental factors influencing their concentration levels. HPLC-facilitated analysis of pigments from Acaryochloris cells cultured under various light quantities was performed; light stress conditions induced an increase in the ratio of MgDVP to Chl d. Pigment analysis of Acaryochloris cells grown under oxygen-stressed conditions demonstrated a decrease in MgDVP levels. We propose that the Chl d biosynthesis pathway favours an aerobic environment despite the fact that Acaryochloris cells can survive under anaerobic conditions.
*email rosanne.quinnell[at]sydney.edu.au for reprint
Kazandjian, A., Shepherd, V., Rodriguez-Lane... more *email rosanne.quinnell[at]sydney.edu.au for reprint Kazandjian, A., Shepherd, V., Rodriguez-Lanetty, M., Nordmeier, W., Salih, A., Cox, J., Larkum, A. W. D., & Quinnell, R. (2008). Isolation of symbiosomes and the symbiosome membrane complex from the zoanthid Zoanthus robustus. Phycologia, 47(3), 294 - 306. The zoanthid Zoanthus robustus was used as a model organism to develop procedures for isolating pure symbiosomes and symbiosome membranes. The symbiosome is comprised of a zooxanthella (Symbiodinium sp.) cell that divides rarely and is separated from the host gastrodermal cytoplasm by a symbiosome multimembrane complex. Devising a method to isolate membranes at the interface between the symbiotic partners is a critical first step in characterising the molecular components involved in the metabolic trafficking necessary to sustain an effective symbiosis. After zoanthid gastrodermal cells were extracted, symbiosomes were released by mechanical disruption, recovered by centrifugation, and then purified using discontinuous sucrose gradient centrifugation. The material forming the membrane complex around symbiosomes proved highly resistant to disruption. Methods used to dissociate this interface from symbionts included (1) Triton X-100 detergent solubilisation, (2) osmotic shock with mechanical disruption, and (3) vigorous mechanical disruptions, where powerful shearing forces were used, combined with a series of sucrose density gradient centrifugation steps. The lipophilic styryl fluorochrome FM 1-43, at a concentration of 30 µM, selectively labelled the symbiosome membrane complex, both for isolated symbiosomes and those in hospite. Other cell membranes, including plasma membranes, endoplasmic reticulum, tonoplast, and organelle membranes, were not visibly labelled at this concentration. The selective labelling of the symbiosome membrane complex remained stable even after long exposure times (3 h). At 30 µM concentration, FM 1-43 also labelled symbiosome membrane fragments isolated using methods (1), (2) and (3). Method (3) proved to be the most effective in producing a fraction enriched in FM-143-labelled membrane material, which we call a symbiosome membrane complex. Transmission electron microscopy, together with confocal and conventional epifluorescence microscopy of the FM 1-43-stained preparations, was used to validate the purity of symbiosome preparations and to infer the complexity of the symbiosome membrane complex. This membrane complex has regions where the membranes contributed by the alga are appressed, and punctate regions whose function remains unclear. http://imageslab.fiu.edu/sites/default/files/phycologia2008.pdf "
Chlorophyll (Chl) d is the major pigment in the photosystems (PS) and light-harvesting complex(es... more Chlorophyll (Chl) d is the major pigment in the photosystems (PS) and light-harvesting complex(es) of Acaryochloris marina. Chl a is present in small and variable amounts in PSII and in the light-harvesting complex(es). Isolated PSII complex showed a major fluorescence emission peak at 725 nm and a smaller emission peak due to Chl d at 701 nm, while the PSI complex showed two pools of Chl d, one with emission at 730 nm and the other at 709 nm at 77 K. In PSI and PSII of classical cyanobacteria and of higher plants, where Chl a is the predominant pigment rather than Chl d, these differences are not as pronounced. Light energy absorbed by phycobiliproteins was also active in these Chl d emissions. The major light-harvesting pigment protein is similar to the prochlorophyte Chl-binding protein (pcb) and had a major emission peak at 711 nm. In Cyanobacteria an iron-stress induced Chl-binding protein (isiA) forms a polymeric ring around PSI, and so the effect(s) of iron stress on A. marina where investigated. No clear evidence could be deduced for the formation of an isiA protein under iron stress and no clear changes in the proportion of Chl d :Chl a could be discerned although phycobilins showed a decreased under iron-stress conditions. That Chl d replaces Chl a in all its functions in A. marina is clear; the advantage of this evolutionary development appears to be to enable A. marina to absorb far-red light which occurs in environments where red light is filtered out by other photosynthetic organisms.
Fast responding voltage sensitive dyes, RH421 and di-4-ASPBS, were used to study the electrogenic... more Fast responding voltage sensitive dyes, RH421 and di-4-ASPBS, were used to study the electrogenic properties of plant plasma membrane proton pumps on sealed plasma membrane vesicles extracted by two-phase partitioning from Beta vulgaris and Avena sativa cv Swan root material. Fluorescence spectroscopy in the presence of the dye RH421 (10.8 nM) was sufficiently sensitive to detect electrogenic activity of the extracted plant vesicles. The dye detection system could detect inhibition of electrogenic activity of vesicles by vanadate (75 μM) and stimulation by nigericin (0.5 μM). The newly developed dye di-4-ASPBS was less sensitive to detecting the electrogenic proton pump activity. This study represents an important innovation in plant biophysics as this class of fast responding voltage sensitive dyes have never to our knowledge been used to study electrogenic proton pump activity derived from plant membranes and represents a novel approach for carrying out such studies.
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Papers by Anthony Larkum
Kazandjian, A., Shepherd, V., Rodriguez-Lanetty, M., Nordmeier, W., Salih, A., Cox, J., Larkum, A. W. D., & Quinnell, R. (2008). Isolation of symbiosomes and the symbiosome membrane complex from the zoanthid Zoanthus robustus. Phycologia, 47(3), 294 - 306.
The zoanthid Zoanthus robustus was used as a model organism to develop procedures for isolating pure symbiosomes and symbiosome membranes. The symbiosome is comprised of a zooxanthella (Symbiodinium sp.) cell that divides rarely and is separated from the host gastrodermal cytoplasm by a symbiosome multimembrane complex. Devising a method to isolate membranes at the interface between the symbiotic partners is a critical first step in characterising the molecular components involved in the metabolic trafficking necessary to sustain an effective symbiosis. After zoanthid gastrodermal cells were extracted, symbiosomes were released by mechanical disruption, recovered by centrifugation, and then purified using discontinuous sucrose gradient centrifugation. The material forming the membrane complex around symbiosomes proved highly resistant to disruption. Methods used to dissociate this interface from symbionts included (1) Triton X-100 detergent solubilisation, (2) osmotic shock with mechanical disruption, and (3) vigorous mechanical disruptions, where powerful shearing forces were used, combined with a series of sucrose density gradient centrifugation steps. The lipophilic styryl fluorochrome FM 1-43, at a concentration of 30 µM, selectively labelled the symbiosome membrane complex, both for isolated symbiosomes and those in hospite. Other cell membranes, including plasma membranes, endoplasmic reticulum, tonoplast, and organelle membranes, were not visibly labelled at this concentration. The selective labelling of the symbiosome membrane complex remained stable even after long exposure times (3 h). At 30 µM concentration, FM 1-43 also labelled symbiosome membrane fragments isolated using methods (1), (2) and (3). Method (3) proved to be the most effective in producing a fraction enriched in FM-143-labelled membrane material, which we call a symbiosome membrane complex. Transmission electron microscopy, together with confocal and conventional epifluorescence microscopy of the FM 1-43-stained preparations, was used to validate the purity of symbiosome preparations and to infer the complexity of the symbiosome membrane complex. This membrane complex has regions where the membranes contributed by the alga are appressed, and punctate regions whose function remains unclear.
http://imageslab.fiu.edu/sites/default/files/phycologia2008.pdf "